Miners saw a flash of white in the rock. It was an Ice Age mammoth tusk.

It was pitch dark in a North Dakota mine and the coal miners were up late, working through an early morning shift on the Sunday of Memorial Day weekend. But as a bulldozer operator approached a pile of excavated debris, he was attentive enough to see his headlights catch an unusual flash of white among the dirt and rock.

He paused before sending the dozer forward and alerted the rest of his team.

Sitting in the pile of rock – and somehow intact after being excavated and transported across the mine by heavy machinery – was the tusk of a mammoth that had been buried since the Ice Age. Its discovery by workers at Freedom Mine, a surface coal mine near Beulah, North Dakota, in May shocked state researchers and brought paleontologists and miners together to turn the mine into an archaeological dig site. Their work uncovered more than 20 additional bones, one of the largest discoveries of mammoth remains in the state, the North Dakota Department of Mineral Resources announced this month.

“You don’t really expect to see this full curved tusk just laying there in perfect condition after being dumped out of the back of a dump truck,” Clint Boyd, senior paleontologist for the North Dakota Geological Survey, told the Washington Post.

Mammoths roamed North America tens of thousands of years ago, and skeletal discoveries of the mighty Ice Age beasts have excited communities across the United States. But their remains are not distributed evenly. While South Dakota boasts a bustling excavation site and tourist attraction near the city of Hot Springs that has unearthed the remains of more than 60 mammoths, researchers have struggled to find comparable collections of mammoth bones in neighboring North Dakota.

“For whatever reason, we haven’t found a lot of good specimens out of there,” Boyd said. “Most specimens are just a bone or two or three and that’s it.”

It would have stayed that way if not for the sharp eyes of the crew working the graveyard shift at Freedom Mine that holiday weekend.

Miners are instructed to stay on the lookout for historic artifacts or remains as they dig, said David Straley, the vice president of external affairs for North American Coal, which oversees the mine. But the discovery was still a stroke of luck. Somehow, the tusk had survived its trip through Freedom Mine’s digging operation in the scoop of a massive mining excavator and a dump truck bed without getting damaged. It was spotted by the bulldozer operator just before it likely would have been crushed or buried in a pile of debris.

“The coal miners did exactly what they were supposed to do,” Straley said. “And we’re just extremely proud of them. And just excited about what turned out of this thing.”

Boyd was alerted to the find the following week. The tusk – around 7 feet long and 120 pounds, Straley estimated – was an impressive find on its own. But it also led Boyd and a team of researchers to further discoveries at the mine.

In several visits over the following months, paleontologists conducted further digs around where the tusk was excavated and discovered signs of a prehistoric stream and more mammoth bones scattered along the stream’s path, Boyd said.

Those details could only hint at the circumstances of the mammoth’s death in a vastly different Ice Age environment – did it drown in the water? Or were its remains washed into the stream by a flood? – and also meant that the mammoth’s remains were incomplete. But Boyd said he was pleased the team found additional bones, including ribs, a shoulder blade and a tooth.

The real prize, though, was the tusk, which Boyd said he was shocked to discover was intact after churning through Freedom Mine’s machines.

“The tusks, because they’re so heavy and dense, tend to be kind of fragile under their own weight,” Boyd said, “… so that I was definitely surprised.”

The mammoth remains are being cleaned and stabilized at the North Dakota Heritage Center & State Museum in Bismarck, according to the Department of Mineral Resources. Afterward, they will be put on display. The tusk and bones won’t quite rival South Dakota’s collection of mammoth skeletons, but it’s a start.

“It’s the best Ice Age specimen that I’ve worked on, personally,” Boyd said.